1. Field of the Invention
The present invention relates to an apparatus and method for driving a stepping motor.
2. Related Background Art
FIG. 9 is a block diagram, partly in circuit diagram, showing a configuration of a conventional apparatus for driving a two-phase stepping motor by utilizing the bipolar driving. In the figure, reference numeral 110 designates a two-phase stepping motor which includes, in its inside, a coil LA101 of a phase A, a coil LB102 of a phase B, and a magnetized rotor 103. Reference symbols 120A+, 120A−, 120B+ and 120B− designate half bridge circuits, respectively. Then, there are provided a pair of half bridge circuits for the phase A coil LA101, and a pair of half bridge circuits for the phase B coil LB102, i.e., four half bridge circuits in total. Reference numeral 130 designates a control circuit for controlling a driving signal for the half bridge circuits 120A+ and 120A−, and a driving signal for the half bridge circuits 120B+ and 120B−.
Each of the half bridge circuits 120A+, 120A−, 120B+ and 120B− is a push-pull circuit. The push-pull circuit is changed between a state in which a current is caused to flow out to a terminal (push state) and a state in which a current is pulled through the terminal (pull state) in accordance with a control signal issued from the control circuit 130. Then, the four half bridge circuits 120A+, 120A−, 120B+ and 120B− are changed successively between the push state and the pull state, whereby the poles of the phase A and the phase B are changed over to each other to rotate the rotor 103 stepwise.
In the case of the above-mentioned prior art, four half bridge circuits are required in total, and hence four driving lines to be connected to the coils are also required in total. Then, a large number of two-phase stepping motors utilizing the bipolar driving may be used depending on the apparatuses in some cases, and hence a simple increase in number of half bridge circuits and number of driving lines exerts an influence on the shape, the design and the like of the apparatus.